1. Field of the Invention
Embodiments of the present invention relate to optimized power systems that utilize geothermal heat sources.
More specifically, embodiments of the present invention relate to optimized binary power systems called organic Rankine cycles (ORCs) utilizing a flow of geothermal fluid as a heat source.
2. Description of the Related Art
Typical geothermal fluids or geofluids are highly mineralized, which limits the minimum temperature to which the geofluids may be cooled to provide heat for a geothermal power system. If it is cooled further than this limit, the minerals in the geofluids will deposit on heat exchange apparatus surfaces or other surfaces in contact with the geofluids, fouling them and interfering with the operation of the power system.
At the same time, the greater the degree of utilization of the heat source stream (i.e., the closer the final temperature of the heat source stream is to the minimum temperature limit imposed by the geofluids mineralization) the higher the output of the system.
However, all actual power systems in current operation do not work so as to make maximum allowable utilization of their heat sources. This is because the temperature of the cooling medium (air or water) varies over the course of each day, as well as by season and in response to the weather. Thus, the working fluid enters and exits the system's feed pump with different temperatures, depending on the coolant temperature.
All of the heat available from a given heat source may be conceptually divided into two portions; the heat used for the vaporization of the working fluid and the heat used for the pre-heating of the working fluid from the temperature at the point just after the feed pump up to the boiling temperature of the working fluid.
In real-world operation, the systems must operate so that, even on the coldest day (corresponding to the coldest possible temperature of the cooling medium), the exit temperature of the heat source always remains above the limit imposed by issues of mineralization.
Therefore, in real-world operations of a power system, the parameters are chosen so that the final temperature of the heat source stream will be measurably higher than the limit imposed by mineralization in all cases, where the temperature of the cooling medium is higher than the coldest it can be. As a result, in an actual installation, most of the time the heat source is not fully utilized.
Thus, there is a need in the art for optimized systems utilizing geothermal fluids (geofluids) as a heat source.